The invention relates to a fuel supply assembly and more specifically to a positive displacement pump for a fuel supply assembly and formed as an internal gear pump comprising a ring gear having internal teeth that cooperate with external teeth of a pinion to form expanding and contracting pumping chambers, and outer support means for supporting the ring gear. Such an assembly is disclosed in DE-OS 3,105,547 corresponding to U.S. Pat. No. 4,401,416. In the assembly disclosed therein, the outer support means comprises circular guide plate for guiding the ring gear. The inner surface of the circular guide plate defining its bore slidably engages the ring gear so that the ring gear rotates without any play. The tolerances should be so selected that the ring gear of the gear pump is not damaged. This would require very close tolerances which can be obtained only by high precision finishing operations which substantially increase the costs of manufacturing the pump.